Cutting tool for parting and similar operations

ABSTRACT

A parting tool includes a thin holder forming a groove open at one end, and a double-ended cutting insert mounted in the groove. The insert includes front and rear cutting edges and a rear end surface abutting against a rear support surface of the groove. The rear support surface is configured to enable differently shaped double-ended inserts to be mounted therein without the occurrence of contact between the rear cutting edge and a surface of the holder.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a tool for parting or similar turningby operations of the type which includes a holder in the shape of arather thin disc or disc-shaped member of a first material, such assteel, and a cutting insert of a second harder material, such ascemented carbide, wherein at least the front portion of said holderblade is provided with an outwardly open recess. The recess is mainlydefined by a lower bottom surface, an inner or rear wall and an upperwall integral with an elastically flexible arm intended to clamp theinsert into its recess, whereby the insert has both upper and lowerV-shaped edges intended to cooperate with correspondingly V-shapedridges or recesses in connection with said recess.

BACKGROUND OF THE INVENTION

During repeated parting and grooving it is of special importance thatthe tool has a well defined axial support surface against which the rearend of the insert can be supported. It is another demand that the heightof said surface is not too large so as to cause damaging surface contactwith a zone close to the active corner of the cutting insert in case ofusing double-ended inserts. One of the drawbacks with the presentcommonly used blade holders is that they do not provide an appropriateaxial support to more than one type of inserts. Each time when theoperator needs to change inserts to another type with another type ofcutting portion having another inclination angle at the clearancesurface below the cutting edge he must also change the blade harder.Hence, there is a need of a new type of blade holder suitable to receiveseveral different types of inserts.

SUMMARY OF THE INVENTION

The present invention relates to a new type of blade holder wherein theinsert-receiving recess of the holder comprises a rear axial supportwith such formation inserts with widely varying inclination angles ofthe clearance surface below the cutting edge can be received therein.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become apparent fromthe following detailed description of a preferred embodiment thereof inconnection with the accompanying drawing in which like numeralsdesignate like elements, and in which:

FIG. 1 is a partial perspective view of a cutting tool of the inventionwith an insert mounted in place in a blade shaped holder;

FIG. 2 is a side view of the tool of FIG. 1;

FIG. 3 is a side view of the blade holder of FIGS. 1-2 without anyinsert;

FIG. 4 is a perspective enlarged view of the bottom and inner walls ofthe insert receiving recess; and

FIG. 5 is an enlarged view showing the insert after being mounted intothe tool.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The parting tool of FIG. 1 comprises a blade type holder, in itsentirety designated 1, and a cutting insert 2. The insert 2 can incertain cases be supported against a separate shim plate (not shown).The holder 1 is in the shape of a rather thin disc or blade shapedportion made of steel or similar material. In practice said blade holderis often rectangular, elongated, and has at least one of its oppositeends provided with an upper clamp arm 3 integral with the holder whilsthaving an outwardly open recess 4 (see FIG. 3) which is mainly confinedby a bottom wall 5, an inner or rear wall 6 and an upper wall 7 which ispart of the elastic movable clamp arm 3 of said blade holder provided tofasten the insert into its recess. In the embodiment shown as an examplein the drawings the blade holder 1 has a slot 8 the end of which issmoothly rounded. The purpose of this slot is to provide a certainamount of elasticity to the clamp arm 3 and to provide a certain spacefor the cutting edge and the insert portion below said cutting edge on adouble-ended insert such that damaging surface contact does not occur.The arm 3 could alternatively, due to its resilience, in a manner knownper se, be pivoted downwards towards the bottom wall of the recess bymeans of a separate clamp screw (not shown).

The insert 2 as shown in FIGS. 1-2 is made of a cemented carbide bodythe front end of which has a main cutting edge 9, next to which there isprovided a chip breaker surface 10 on the upper surface of said body. Inthe area behind the chip breaking portion 10 there is a raised portionof said insert body that is provided with a recess 11 V-shaped incross-section and divided into forward and rear portions 11′ and 11″respectively between which there is a central groove with concaverounded form (not shown). The lower side of said insert body 2 is alsoprovided with a groove 12 V-shaped in cross-section. In practice bothgrooves on said upper and lower sides could have an identical V-shapedformation.

Although the cutting edge 9 in the example as shown extendsperpendicular to the longitudinal extension of the insert, the form andlocation of the edge could be widely varied. That is, the insert can beprovided with circularly rounded or partially rounded edges, and if theedge is straight it could be inclined in relation to the longitudinalextent of the insert.

According to the invention the straightly upstanding portion of a rearsupport surface of the insert 2 is arranged to be supported against arear straightly upstanding wall 6 that is integral with the blade holderin said recess. This support wall 6 extends via a convexly curvedsurface 14 into a curved end portion 15, 8 a made by groove milling intothe rear slot 8. The detailed embodiment is preferably such that therear portion of the bottom wall 5 extends into a milled groove 5 ahaving a smoothly rounded contour, which then extends into the supportwall 6 approximately at the inflexion point 13. By this embodiment it isensured that both the rear, lower and upper edge portions of the insertbecome freely exposed from, i.e., out of contact with, said bladeholder. The upstanding support wall 6 can be planar, preferably with aheight less than its width whereby said support wall 6 only needs tohave a relatively limited height extension as shown in FIG. 4.Alternatively, however, the rear insert surface 2 a that is intended forcontact with said support wall 6 could be provided with a V-shapedrecess and the support wall 6 can have a male extension such that saidextension and said V-shaped groove form a male female joint.

As best appears from FIG. 5, the detailed embodiment is such that theaxial support wall 6 extends upwards and extends into a convexly shapedtransition surface 14 of relatively large radius R₁ which extends into aconvex partial surface 15 with essentially smaller radius R₂. Thispartial surface 15 then extends into groove 8 confined by a concavesurface 8 a with a radius R₃ which in this shown embodiment is largerthan both above mentioned radii R₁ and R₂. In certain cases, however, R₁could be larger than R₃. The radius R₃ ought to be equal to orpreferably larger than radius R₄ of said groove 5 a. Thanks to thisembodiment it is possible to receive in the same blade holder the insert2 shown in FIGS. 1-3 the rear end surface of which comprises a lower endsurface 2 a on the insert that extends perpendicularly from the bottomwall 5 and an upper clearance surface 2 b. This last mentioned clearancesurface 2 b is hereby freely exposed from the rear support wall 6. Inthe same holder can also be received an insert with the form having thedashed appearance A as shown in FIG. 5. As appears from FIG. 5 thisinsert has a form that deviates both in its lower and upper portion.Thus, lower surface portion A₁ of said dashed appearance A has an acuteclearance angle α that amounts to 45° whereas the upper surface portionA₂ has been provided with a substantially smaller clearance angle β. Inspite of these geometrical differences this insert can be well receivedin the same blade holder as the insert shown in FIGS. 1-2. The reason isthat the lower sharply inclined clearance surface portion A₁ can have anappropriate support against the upper portion of the convexly shapedsurface 16. The size of R₁ ought to be in the range 0.2-100 mm,preferably 0.5-5 mm whereas R₂ ought to be in the range 0-10 mm,preferably 0.2-2 mm. The size of R₃ ought to be 0.2-10 mm, preferably0.2-5 mm whereas the size of R₄ ought to be 0.5-5 mm, preferably 1-5 mm.

The number of blade holders can hereby be essentially reduced for acustomer that needs a number of differently shaped inserts dependingupon which type of grooving and type of workpiece material to be usedwhich is a commonly occurring situation in the machining industry.

Various embodiments of the above example can of course be used withinthe scope of e invention. For instance, it is not necessary that thesupport wall 6 extends perpendicularly from the bottom wall 5. Also, itis to be understood that the transition surface 14 can be composed of anumber of surface segments with respective radii of varying size.

What is claimed is:
 1. Metal cutting tool for parting comprising a thinholder formed of a first material, and a double-ended cutting insertformed of a second harder material, wherein the holder is provided witha forwardly open recess, the recess including a bottom wall, a rearwall, and an upper wall comprising part of an elastically movableclamping arm integral with the holder to frictionally secure the insertin the recess, the insert including upper and lower surfaces engagingthe upper and bottom walls, respectively of the recess by respectiveridge-and-groove connections of generally V-shaped cross section, therear wall of the recess defining a support surface including astraightly upstanding upper part against which a straightly upstandingportion of a rear end surface of the insert abuts, the support surfaceextending upwardly from the bottom wall of the recess, the upper part ofthe support surface transforming into a first convexly shaped surfacehaving a first radius, the first convexly shaped surface transforminginto a second convexly shaped surface having a second radius smallerthan the first radius, the second convexly shaped surface transforminginto a concavely curved surface which defines a rear end of an extensionof the recess.
 2. The tool defined in claim 1, wherein a lower portionof the supporting surface transforms into a groove having a smoothlyrounded contour, the groove interconnecting the supporting surface withthe bottom wall of the recess.
 3. The tool according to claim 2, whereina radius of the concavely curved surface is no smaller than a radius ofthe groove of smoothly rounded contour.
 4. The tool according to claim3, wherein the rear end surface of the insert includes a V-shapedrecess, and the support surface being provided with a correspondingV-shaped extension projecting into the V-shaped recess to form amale-female joint therewith.